Added Resource::Contact
Added Mapper::Contact
Refactor ContactClient#contacts to use resource and mapper
Added Resource::Contact#find_by_external_key
Replace Client#contacts method with delegation statement
Add contact by external key query to client
Remove unused code from ContactClient
Move ContactClient spec into correct folder scope
Move Client spec into correct folder scope
Merge pull request #19 from anderslime/contact-refactoring

Added method to find contact by the external key